FRP drive shafts are made by joining two metal end joints to either end of an FRP (Fiber Reinforced Plastics) cylinder and have the advantage of being lightweight. However, how to increase the joint strength between the FRP cylinder and each end joint has been a technical problem to be solved, and various proposals have been submitted for solving this problem.
FIGS. 7A and 7B show an FRP drive shaft 1 that is disclosed in Patent Literature 1. The FRP drive shaft 1 is provided with an FRP cylinder 2, two end joints 3 made of metal which are joined to either end of the FRP cylinder 2, and two outer collars 4, each of which is fixed to an outer periphery of the FRP cylinder 2. In these drawings, only a portion of the FRP drive shaft 1 in the vicinity of one end of the FRP cylinder 2 is shown in the drawing, and hence, the other portion of the FRP drive shaft 1 in the vicinity of the other end of the FPR cylinder 2 is not shown in the drawings.
In the FRP drive shaft 1, to fix the end joints 3 to the FRP cylinder 2, each end joint 3 is provided on an outer periphery thereof with a serrated portion 5, and this serrated portion 5 is press-fitted into an inner periphery of the FRP cylinder 2. In addition, to fix each outer collar 4 to an outer periphery of the FRP cylinder 2, each end joint 3 is provided with an oval-shaped non-circular cross sectional shaft portion 6, an oval-shaped non-circular engaging hole 7 is formed in each outer collar 4, and the non-circular cross sectional shaft portion 6 and the non-circular engaging hole 7 are engaged with each other.